The present invention relates to the field of communications, and more particularly, to phased array antennas.
Antenna systems are widely used in both ground based applications (e.g., cellular antennas) and airborne applications (e.g., airplane or satellite antennas). For example, so-called xe2x80x9csmartxe2x80x9d antenna systems, such as adaptive or phased array antennas, combine the outputs of multiple antenna elements with signal processing capabilities to transmit and/or receive communications signals (e.g., microwave signals, RF signals, etc.). As a result, such antenna systems can vary the transmission or reception pattern of the communications signals in response to the signal environment to improve performance characteristics.
In such antennas, the antenna elements typically have a respective phase shifter associated therewith. The phase shifters may be controlled by a central array controller, for example, to adjust respective phases of the antenna elements across the array. Similarly, transmission and reception amplifiers are also typically coupled to each antenna element and to centralized transmit/receive circuitry to adjust signal transmission and reception strength. The respective phase shifter and transmission/reception amplifiers for each antenna element may be included in an antenna module, for example.
One example of a prior art antenna module is disclosed in U.S. Pat. No. 5,559,519 to Fenner entitled xe2x80x9cMethod and System for the Sequential Adaptive Deterministic Calibration of Active Phased Arrays.xe2x80x9d The antenna module includes a plurality of antenna elements, power amplifiers coupled to the antenna elements, and a pre-amplifier for activating the power amplifiers. A controller is also included which has an output for controlling biasing of the pre-amplifier. The antenna module further includes an attenuator and a phase shifter, and the controller also responds to signals at its input for controlling amplitude at the attenuator and phase at the phase shifter of the antenna element during both transmit and receive modes.
While the above prior art antenna module does include a controller for biasing the pre-amplifier, it does not control the biasing of the power amplifiers. Yet, some phased array elements commonly use monolithic microwave integrated circuit (MMIC) amplifiers, for example, which may require a control voltage to set the bias operating point for the amplifier. This is particularly the case with transmitter amplifiers.
As a result, typical prior art phased array antenna modules include a plurality of resistors, for example, which are arranged to set the bias point. Even so, these resistors are typically fixed resistors installed during manufacture. Further, the same resistor configuration is typically used in each antenna module for convenience, thus the bias value is not individually adjusted for each amplifier. Yet, even small variations in the control voltage, which may still occur with such configurations, can significantly affect amplifier operation.
Another prior art approach to bias adjustment is disclosed in U.S. Pat. No. 6,163,220 to Schellenberg entitled xe2x80x9cHigh-Voltage, Series-Biased FET Amplifier for High-Efficiency Applications.xe2x80x9d This patent is directed to an integrated circuit two-stage power amplifier including a series-connected active biasing network for biasing RF power cells. The biasing network includes series-connected resistors and series-connected buffer cells connected between the series-connected resistors and the RF power cells. The biasing network may also include a programmable resistor for setting a current in the bias array.
While this approach may provide additional flexibility, such amplifiers may add to design complexities and increased costs.
In view of the foregoing background, it is therefore an object of the invention to provide a phased array antenna which provides for controllable biasing of transmitter and/or receiver amplifiers of element control modules thereof.
This and other objects, features, and advantages in accordance with the present invention are provided by a phased array antenna including a substrate and a plurality of phased array antenna elements carried thereby, and an element control module for at least one of the phased array antenna elements. The element control module may include an amplifier coupled to the at least one phased array antenna element and having a controllable bias. The element control module may also include a controllable device coupled to said amplifier and having at least one of a controllable phase, delay, and attenuation. The element control module may further include a control application specific integrated circuit (ASIC) for controlling both the controllable phase, delay, and/or attenuation of the controllable device and the controllable bias of the amplifier.
More specifically, the element control module may further include a resistor network coupled between the control ASIC and the amplifier, and the control ASIC may control the controllable bias of the amplifier via the resistor network. The control ASIC may include at least one bias adjust register connected to the resistor network and control logic circuitry for writing digital bias adjust signals (e.g., digital data values) to the at least one bias adjust register. Alternately, the control ASIC may include a resistor network coupled to the amplifier. Also, the element control module may further include a capacitor connected between the resistor network and a reference voltage to reduce noise coupling into the amplifier.
Additionally, the phased array antenna may further include an array controller connected to the element control module for causing the control ASIC to control the controllable bias of the amplifier. The amplifier may be a transmitter and/or a receiver amplifier, for example.
Another aspect of the invention is for a similar phased array antenna including an element control module including an amplifier coupled to the at least one phased array antenna element and having a controllable bias, a resistor network coupled to the amplifier, and a control circuit for controlling the controllable bias of the amplifier via the resistor network by outputting digital bias adjust signals to the resistor network. More particularly, the control circuit may be implemented in at least a portion of an ASIC. Alternately, the resistor network and the control circuit may be implemented in an ASIC.
The element control module may further include a controllable device coupled to the amplifier and having a controllable phase, delay, and/or attenuation, and the control circuit may also control the controllable phase, delay, and/or attenuation of the controllable device. Furthermore, the control circuit may include at least one bias adjust register connected to the resistor network and control logic circuitry for writing digital bias adjust signals (e.g., digital data values) to the at least one bias adjust register.
Additionally, the phased array antenna may include an array controller connected to the element control module for causing the control circuit to control the controllable bias of the amplifier. The amplifier may be a transmission and/or a reception amplifier. Also, the element control module may further include a capacitor connected between the resistor network and a reference voltage, again for reducing noise coupling into the amplifier.
Yet another aspect of the invention relates to an element control module for a phased array antenna element of a phased array antenna. The element control module may include an amplifier to be coupled to the phased array antenna element and having a controllable bias, and a controllable device coupled to the amplifier and having at least one of a controllable phase, delay, and/or attenuation. The element control module may also include a control ASIC. The control ASIC may control both the controllable phase, delay, and/or attenuation of the controllable device and the controllable bias of the amplifier.
Still another aspect of the invention is for an element control module which may include an amplifier to be coupled to the phased array antenna element and having a controllable bias, a resistor network coupled to the amplifier, and a control circuit. As noted above, the control circuit may control the controllable bias of the amplifier via the resistor network by outputting digital bias adjust signals (e.g., digital data values) to the resistor network.
A method aspect of the invention is for controlling biasing of an amplifier coupled to a phased array antenna element. The method may include using a control ASIC, such as the one described above, for controlling a phase, delay, and/or attenuation of a controllable device coupled to the amplifier, and using the control ASIC for also controlling the bias of the amplifier.
Another method aspect of the invention is for controlling a bias of an amplifier for a phased array antenna element and may include coupling a resistor network to the amplifier. Further, the method may also include controlling the bias of the amplifier using the resistor network by outputting digital bias adjust signals (e.g., digital data values) to the resistor network.